The neat thing about major problems is that they act as a challenge for our greatest intellects. When the automobile replaced the horse (as Frag has testified previously elsewhere) the rate of tuberculosis in the human population of our big cities crashed because we replaced horse poop in the environment with burnt fossil fuel smoke. Looks like we are going to have to do something even cleaner than that if we want to address things like autism and asthma. I agree that "farming" will be most necessary, but it will (is now becoming) very much different than it has been. Think along the lines of the old "victory gardens" only with contemporary technology. There is a fellow who has planted a nut orchard in downtown Detroit, is planning to grow and sell nuts commercially from there. Other folks have designed those 'vertical farms' I keep going on about. We are only just beginning to take advantage of the tools we already have in hand, vastly more can be done for nothing more than making the choice. Plague, war, drought, famine and natural disaster could control the human population much more rapidly. Best bet is bringing "third world" nations into "second world" status, which has proven to drop the birthrate enough.